1. Field of the Invention
This invention relates to means for improving a rate of heat transfer from a high temperature condensable medium and a lower temperature medium flowing through a heat exchanger and more particularly to a unit that may engage an upright positioned tube in a high-capacity heat exchanger to reduce a thickness of condensate film that forms on and then flows down the tube as the condensable medium cools and condenses on the tube.
2. Prior Art
Heat transfer has been studied extensively and is mathematically defined in many learned writings on this subject. Devices for transferring heat come in many forms. For example, in many domestic water heaters high temperature products of combustion from burning natural gas are used to heat cooler tap water. In other devices the high temperature medium may be a condensable vapor such as steam or Freon.
Additionally, such heat exchanging devices often include means to increase the rate of heat transfer. In U.S. Pat. No. 3,837,396 a series of fins are shown attached to a set of tubes. The fins increase the effective area of the tube surface through which heat may pass and therefore the rate at which heat energy may transfer therethrough. Also the tubes may include inner structure for diverting a flow of condensate forming on an inner surface of the tube. This inner structure may have a tree-like shape or be in the form of a series of spaced apart cups.
U.S. Pat. No. 496,757 discloses earlier apparatus for condensable vapor use. In this case a tube of the apparatus includes a set of three, spaced apart wires formed into a downwardly sloped helix that fits about the tube. These wires provide like-shaped, continuous paths for a downward flow of condensate forming on the tube.
U.S. Pat. No. 2,983,115 shows another early example of heat transfer apparatus particularly adapted for a condensable vapor. This apparatus comprises a coil having a set of spaced apart, horizontal tube sections. Each tube section has extended surface elements in the form of a continuous fin spirally formed thereabout. Respective notches in a bottom of the elements define a channel shaped area for a trough. During use condensate forms on each tube and attached elements. This condensate drains down the elements to collect in the respective troughs and then flow away from the coils.
U.S. Pat. No. 3,358,750 sets out still further means for improved transferring of heat. In this case an upright condenser tube has a set of vertically affixed bar elements. During use condensate forming on the tube is drawn by capillary action to fillet areas formed by the tube and a base of each element. Condensate collecting in these fillet areas drains downward.
Lastly, U.S. Pat. No. 4,715,433 discloses a more recent exchanger particularly adapted for cryogenic applications. This exchanger has a series of alternately stacked condensing units and reboiler units. Each condensing unit comprises a pair of spaced apart, vertically positioned plates. Between these plates and attached to an inner side of each is a set of vertically spaced apart, hollow bars positioned on an angle. In a top surface of each bar is a series of openings to receive a downward flow of condensate forming on the plate inner side above that bar. Diversion of the condensate flow by the bars inhibits any excessive condensate build-up on the plates.